I want when onmouseover on particular section to put an OPACITY #fff 0.2 layer on everything except the selected class i.e. table

Similarly as you have:

.tableHighlight:hover{background-color:#eee}
<table id='table-main' class='tableHighlight'>
...

but inversed (puts layer on everything else, but not the table itself)

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http://jsfiddle.net/LYcm9/1/